Journal of Materials in Civil Engineering

In this study, properties of warm mix asphalt (WMA) compacted with various levels of gradation segregation were evaluated in the laboratory. Six segregated gradations were designed to compare with the control gradation and test sections were paved with the control gradation. Then pavement quality indicator (PQI) and field coring were used to evaluate the uniformity of the WMA test sections with the statistical method. In addition, sieve analysis of the cores was conducted to evaluate the level of segregation. The test results show that gradation segregation has a remarkable effect on water stability, high-temperature stability, low-temperature cracking, and tensile strength of WMA mixtures. Statistical analysis results show that the levels of segregation in localized areas are quite typical because the air void contents follow a normal distribution and the mixtures along the central line are denser than other areas. Sieve analyses of the cores show that most places of the typical segregated localized areas in the test sections have no segregation or low-level segregation, so the construction quality is good. It also shows that the air void content increases as the gradation gets coarser, which is consistent with laboratory test results.

The practice of soil treatment using cement and zeolite is an approach that can be widely used in soil stabilization particularly in road construction, as a support layer for shallow foundations, to strengthen slopes, and to prevent sand liquefaction. The present study intends to quantify the impact of cement and zeolite contents, porosity index, porosity/cement and porosity/${\mathrm{SiO}}_2$, and ${\mathrm{Al}}_2{\mathrm{O}}_3$ particles ratios on zeolite-cemented sands by the assessment of splitting tensile strength (${\mathit{q}}_{\mathit{t}}$). A program of splitting tensile tests considering three distinct porosity ratios, four cement contents (2, 4, 6, and 8%), and six different percentages of zeolite replaced by part of cement (0, 10, 30, 50, 70, and 90%) is performed in this study. Results indicate that cement replaced by zeolite at optimum proportion of 30% and the value of improved ${\mathit{q}}_{\mathit{t}}$ of the cement sand specimens because zeolite and cement chemical properties are exploited. Increasing cement content and porosity of the compacted mixture, the efficiency of using zeolite rises. In this paper, it has been shown that for the zeolite-cement-sand mixtures, ${\mathit{q}}_{\mathit{t}}$ increases via cement content (C) raise and porosity ($\eta$) reduction and a power function is well-adapted to fit both ${\mathit{q}}_{\mathit{t}}-\mathit{C}$ and ${\mathit{q}}_{\mathit{t}}-\mathrm{\eta }$. Finally, a key parameter, i.e., ${\mathrm{SiO}}_2$ and ${\mathrm{Al}}_2{\mathrm{O}}_3$ particles as active particles (AP) introduced and six ${\mathit{q}}_{\mathit{t}}-\mathrm{A}\mathrm{P}$ diagrams are drawn, any of which is traced to a specific amount of zeolite. Afterward, ${\mathit{q}}_{\mathit{t}}$ is plotted against 1/AP and η/AP, which is regarded as a controlling parameter of ${\mathit{q}}_{\mathit{t}}$. As a consequence, for each of the zeolite-cement-sand mixtures studied, a target ${\mathit{q}}_{\mathit{t}}$ value could be obtained using a specific correlation by porosity reductions, cement content rises and zeolite variations. This experimental study will introduce an acceptable description of the mechanical parameters that are extensively used in the subgrade and foundation designs.

A synopsis of an experimental program on the development of a sustainable fly ash–slag blended geopolymer mortar (GPM) and lightweight geopolymer concrete (LGPC) is presented. Geopolymer mortar mixes were prepared incorporating industrial by-products and sustainable desert dune sand to study the effect of different mixing variables, including binding materials, curing temperature, and alkaline activator solution composition and content, on the rheological and mechanical performance. Optimum mix designs were then formulated into producing LGPC samples with different binding materials and curing temperature. Lightweight geopolymer concrete specimens exhibited a brittle behavior with a weakened structure due to low-strength lightweight aggregates. Lightweight geopolymer concrete made with dune sand and a fly ash to slag ratio of $3:1$ resulted in the highest compressive strength when cured for 24 h at 60°C. Microstructure characterization of LGPC specimens was also conducted. Scanning electron microscopy and differential scanning calorimetry showed the coexistence of an aluminosilicate hydrate geopolymer gel and aluminum-modified $\mathrm{C}─\mathrm{S}─\mathrm{H}$ gel as the main polymerization reaction products in an amorphous geopolymeric microstructure.

This paper investigates the effects of hybrid micro-macro steel and micro steel blended with synthetic fibers and of the fiber content on key properties of a cost-effective ultrahigh-performance concrete (UHPC). Eleven mixtures are prepared using three types of fibers: micro steel straight fibers (SF), macro steel hooked-end fibers (HF), and polyvinyl alcohol (PVA) fibers. The fiber content of SF is increased from 0 to 5%. At a fiber content of 2%, different combinations of micro-macro steel and micro steel-PVA fibers are considered. The minislump flow of all mixtures is fixed to $280\pm 10\mathrm{mm}$ by adjusting the high-range water reducer (HRWR) dosage to ensure self-consolidating characteristics. The investigated properties include the HRWR demand, plastic viscosity, compressive strengths, tensile and flexural properties, and autogenous shrinkage. The plastic viscosity increases with the steel fiber content. At a fiber content of 2%, increasing the content of PVA or HF increases the plastic viscosity. Compared with the reference UHPC mixture made with 2% SF, the incorporation of 1% SF and 1% HF increases the flexural strength, toughness, and tensile strength by approximately 25, 30, and 20%, respectively, and reduces the autogenous shrinkage by 25%. The addition of 1.5% SF and 0.5% PVA increases the flexural strength and toughness by 10 and 15%, respectively, and decreases autogenous shrinkage by 40%. Increasing the SF content from 2 to 5% does not significantly improve the flexural properties, but notably reduces autogenous shrinkage.

This study aims to investigate the feasibility of utilizing waste rubber as a partial replacement for silica sand in the development of self-consolidating engineered cementitious composite (SCECC). The effects of the percentage of rubber (0–50%), rubber size [crumb rubber (CR) and powder rubber (PR)], and supplementary cementing materials (SCMs) (fly ash, ground-granulated blast-furnace slag, silica fume, and metakaolin) on the fresh and hardened properties of SCECC were studied. The results indicated that both CR and PR had promising potentials to be more economical and environmentally friendly alternative aggregates to develop sustainable SCECC with higher ductility. Although the inclusion of CR negatively affected the fresh and mechanical properties of SCECC, a number of successful mixtures with up to 30% CR could be developed with strengths greater than 40 MPa. The addition of PR showed a better performance in terms of fresh and mechanical properties compared with CR, allowing up to 40% replacement of rubber to be safely used. The inclusion of CR appeared to continuously increase the deformation capacity of SCECC up to 20% replacement level, while PR continued to improve the deformation capacity up to 50% replacement. Combining PR and different SCMs, especially metakaolin, allowed higher percentages of rubber to be used, achieving semi-lightweight concrete with adequate mechanical properties for multiple structural applications.

PmB 25 A and PmB 45 A Gußasphalts (poured asphalts) are commonly used to pave orthotropic steel bridge deck surfaces, especially in Germany, because they are light, stiff, and easily applied. The behavior of asphalt is time- and temperature-dependent, so the stress-strain relationship is represented mathematically using viscoelasticity. Asphalt mixtures are not homogeneous but are composite mixtures, and the tensile and compression components of their stiffness moduli must be determined separately. Here, the time- and temperature-dependent stiffness moduli of PmB 25 A and PmB 45 A Gußasphalts are derived using indirect tensile test and a new method to allow the creep compliances and relaxation moduli of PmB 25 A and PmB 45 A Gußasphalt types to be determined at 25 and 40°C.

Use of admixtures to improve the engineering behavior of soil is a popular ground improvement technique. Fly ash and tire crumbles are industrial wastes that can be used for the improvement of the engineering behavior of soil. In the present study the compaction and strength behaviors of kaoline clay mixed with tire waste and fly ash alone and in combined forms are studied. To evaluate the compaction behavior, a modified Proctor test was used, and for strength behavior, California bearing ratio (CBR) tests were conducted. Test results have shown that with the inclusion of fly ash and tire crumbles maximum dry density decreases and optimum moisture content increases. In cases in which fly ash and tire crumbles were used alone, a maximum of five-fold and three-fold improvement over CBR values were observed, respectively. But when both fly ash and tire crumbles were used together as admixtures, a 10-fold improvement over the CBR value of clay was observed.

Lignin is an industrial by-product, stockpiles of which are rapidly increasing worldwide due to growing demand. Highway subgrade construction has been identified as one of the viable answers to consume huge quantities of lignin as an environmentally friendly, low-cost, and less energy intensive chemical additive for soil stabilization. This paper presents a systematical laboratory investigation on physical, geomechanical, and microstructural characteristics of lignin-stabilized silty soils. A traditional soil stabilizer, quicklime, was selected as a reference binder for comparison purposes. A series of macroscale laboratory tests were conducted to examine the Atterberg limits, particle size distribution, compaction behaviors, unconfined compressive strength, California Bearing Ratio, and resilient modulus of lignin-stabilized soils. In addition, soil pH, scanning electron microscopy, mercury intrusion porosimetry, X-ray diffraction, and Fourier transform infrared resonance analyses were carried out to explore the mechanisms controlling the changes in engineering properties of lignin-stabilized silty soil. The study reveals that the level of lignin content has a considerable influence on the mechanical properties, particle size distribution, and pore volume of the stabilized silty soil. The optimum lignin content for silty soil is approximately 12% in this study. With the same curing time and compaction conditions, 12% lignin-stabilized silty soil possesses superior mechanical performances compared with the 8% quicklime-stabilized one. The precipitated lignin-based cementing material, which bonds soil particles closely together and fills the pores to produce a more stable soil structure, is the controlling mechanism for the superior mechanical performance of lignin-stabilized soils. Theoretical simulation of the pore size distribution curves demonstrates that the lignin-stabilized silty soil exhibits bimodal type when the lignin content is less than 8%, whereas it displays unimodal type when the lignin content further increases. The reduction in crystalline size and the variation of functional groups for lignin-stabilized soils confirm that electrostatic reaction as well as ionic binding takes place during the process of stabilization.

This paper evaluates a nonmicrobial means of carbonate precipitation to heal cracks in concrete. Enzyme-induced carbonate precipitation (EICP) that relies on plant-derived urease enzyme is used to catalyze the reaction between calcium chloride and urea to precipitate calcium carbonate. The faster rate of carbonate precipitation and the absence of microbes makes this method attractive for surface applications for crack healing of concrete. Notched mortar beams in which precracking is induced are subjected to EICP solutions with different ${\mathrm{CaCl}}_2$ concentrations and a fixed molar ratio of $\text{urea}:{\mathrm{CaCl}}_2$ of 1.2. X-ray diffraction and thermal analysis of samples collected from the vicinity of the notch clearly demonstrate the presence of calcium carbonate in the cracks. A flexural strength enhancement of approximately 33% is observed for mortars treated with an EICP solution made using 0.5 M ${\mathrm{CaCl}}_2$ compared with the mortars that are just moist cured, and the fracture toughness doubled. The strength and fracture parameters (fracture toughness and critical crack tip opening displacement) scale well with the carbonate content. Digital image correlation (DIC) is used to quantify the reduction in crack extension after the beams are treated with the EICP solution.

Reflective cracking is a major phenomenon leading to premature failure of fresh asphalt overlays. Application of a geosynthetic interlayer system to retard reflective crack propagation is a well-known technique. However, this method often fails because of debonding or inadequate interaction between the asphalt and the geosynthetic. Major variables that control the overall performance of paving fabric are the mechanical properties and the asphalt retention capacity. Some of the natural geotextiles (jute and coir) have good mechanical properties comparable with those of synthetic paving fabrics and hence can be advantageously considered in overlay applications. In the present study, various mechanical properties of both natural and synthetic textiles are evaluated and compared with the specifications given by various standard organizations. The results showed that the properties of jute woven geotextiles and coir open grids meet the minimum specifications for them to be used as paving fabrics as per the relevant guidelines. On the other hand, the properties of nonwoven jute and coir geotextiles did not meet the minimum requirements. This paper discusses the different materials and the laboratory techniques employed to evaluate their suitability for pavement applications.

Internal curing (IC) technology using prewetted lightweight aggregates (LWAs) as additives has been proven to be an effective means for mitigating both autogenous shrinkage and early-age cracking under sealed curing conditions. However, for structures in the field, concrete experiences more complex environmental conditions. To better utilize internal curing technology for durable concretes, this study conducts investigations on both normal and internally cured concretes in terms of the microstructure of the interface transition zone, the chloride permeability by electrical method, the ingress depth by ${\mathrm{AgNO}}_3$ spraying, and the strength development after being soaked in single salt solution as well as a complex solution of salt and acid. It was found that the internally cured concrete has similar permeability and resistance to the chloride ion ingress as the normal concrete. The diffusion rate of chloride ions is greater in the complex solution than in the single salt solution. The acid environment increases the ingress depth of chloride ions in both normal and internally cured concretes. In the same solution, internally cured concrete shows less strength loss than the normal concrete. The results in this study are beneficial for producing internally cured concrete with enhanced durability for infrastructure applications.

Warm mix asphalt (WMA) technology is used to reduce mixing and compaction temperature of the binder; however, such addition is also expected to influence the rheological response of the binder during pavement service. This investigation is focused on WMA binders produced using Evotherm (Evotherm-VG30) and Sasobit (Sasobit-VG30) with a base binder (VG30). Shear rate sweep tests and steady shear tests conducted in the temperature range of 100–155°C indicate that the addition of Evotherm and Sasobit consistently reduce the viscosity of binder. This change in viscosity is found to be temperature and aging dependent. Short-term aged Evotherm-VG30 and Sasobit-VG30 binders exhibited increased shear thinning in the compaction temperature regime. Oscillatory shear tests and repeated creep and recovery tests were conducted in the temperature range of 15–75°C. The relationship between dynamic modulus and phase angle of WMA and VG30 binders followed Kramers-Kronig relations. Addition of Sasobit and Evotherm did not change the temperature regime associated with viscoelastic solid-fluid transition. From the creep and recovery test, addition of Evotherm and Sasobit resulted in increased strain during creep at higher temperatures. The influence of additives, especially Sasobit, on the base binder was found to be strongly temperature dependent.

This paper presents the results of experimental studies of the mechanical and physical properties of reprocessed polyethylene (PE) waste as reinforcement in laterite bricks for sustainable building applications. The bricks are produced with different volume fractions of polyethylene. The flexural and compressive strengths and the fracture toughness values of the bricks differ upon curing at room temperature for 28 days and immersing in water (for 24 h, 1 week, and 2 weeks) before complete curing for 28 days. The composite containing 20% by volume PE has the best combination of flexural strength ($\sim 8.2\pm 0.01\mathrm{MPa}$), compressive strength ($\sim 5.5\pm 0.02\mathrm{MPa}$), and fracture toughness ($\sim 0.94\pm 0.03\mathrm{MPa}\surd \mathrm{m}$) after curing in water for 2 weeks. The flexural and compressive strengths and the fracture toughness values are $\sim 4.4\pm 0.03\mathrm{MPa}$, $1.9\pm 0.03\mathrm{MPa}$, and $0.52\pm 0.02\mathrm{MPa}\surd \mathrm{m}$, respectively, for the composite containing 30% by volume PE after curing the bricks in air. The composites containing 10, 20, and 30% by volume PE, respectively, have initial rates of water absorption of $\sim 1.0$, $\sim 1.2$, and $\sim 1.4\mathrm{kg}/{\mathrm{mm}}^2/\min$. The composite containing 20% by volume PE is more resistant to erosion than the composites containing 10 and 30% by volume PE.

Inclusion of alkali-activated municipal slag cement–fly ash as a cement substitute can have an important outcome on the fresh mixtures and early-age strength of geopolymer mortar cured in different conditions. This study evaluates the effects of various quantities of activator on the workability and early-age strength of alkali-activated municipal slag–fly ash–based geopolymer mortar. Early-age compressive strength is measured under different curing conditions: steam curing, water curing, and air curing. In addition, early-age splitting tensile strength, flexural strength, and microstructure analysis using scanning electron microscopy (SEM) are examined for steam-cured mortar. Test results show that both curing regime and activator content in the main binder are significant factors influencing the performance evaluation of fresh mixtures and early-age strength of geopolymer mortar. A standard design equation is used to predict the compressive strength, and predications of splitting tensile and flexural strength of geopolymer mortar are calculated using another standard.

The study focused on two new laboratory procedures developed for the determination of crumb rubber content of asphalt rubber binders. The first methodology was on the basis of the comparative analysis of cobalt and antimony content of base bitumen, crumb rubber, and asphalt rubber. The second was on the basis of the analysis of combustion products of asphalt rubber binders and of their components. Investigations were performed on binders prepared in the laboratory or sampled at production plants during pavement rehabilitation works. Obtained results were encouraging because it was found that both procedures were characterized by satisfactory levels of accuracy and precision.

The passivation capability and long-term chloride-induced corrosion behavior of a low-cost low-alloy (LA) steel and the conventional low-carbon (LC) steel in a simulated concrete pore solution (SCPS) were investigated using various electrochemical techniques and microstructural characterization methods. The results show that the passivation capability of LA steel is slightly higher than LC steel. However, after long-term exposure to SCPS with chlorides, the corrosion resistance of LA steel is superior to LC steel. It is proposed that the high corrosion resistance of LA steel is mainly achieved by the formation of a compact and adherent rust layer on the steel surface.

In the quest to develop a green cement composite with the lowest possible carbon footprint and the highest possible use of industrial by-products, an experimental investigation was undertaken, replacing 100% of ordinary portland cement. This paper presents the results of an experimental program to develop a zero-cement composite, incorporating 2.5, 5, and 7.5% nanosilica, 72.5, 70, and 67.5% fly ash, 25% ground granulated blast furnace slag (GGBFS), and hydrated lime used as a cement additive at 10 and 15% of the total supplementary cementitious material. Compressive strength tests were undertaken to study the mechanical properties of mortar samples of various mix designs. In addition, scanning electron microscopy, thermogravimetry, and X-ray diffraction were undertaken in conjunction with quantitative phase analysis to investigate the various physicochemical changes taking place within the cement matrix and to formulate strategies for its further development. The results demonstrate that the addition of nanosilica and hydrated lime to low calcium/high-volume fly ash and GGBFS blend can help in achieving an environmentally friendly zero-cement composite without the need of any heat treatment. The optimum content of nanosilica was found to be 5%. With the further increase in nanosilica content, although the pozzolanic reaction and the resulting $\mathrm{C}─\mathrm{S}─\mathrm{H}/\mathrm{C}─\mathrm{A}─\mathrm{S}─\mathrm{H}$ gel formation increases, it also increases the microcracking within the cement matrix, resulting in the reduction in compressive strength at both 7 and 28 days of curing. The siliceous hydrogarnet formed as a result of the pozzolanic reaction of amorphous silica (FA, GGBFS, NS), with the calcium aluminate present in GGBFS, shows very poor crystallinity with no visible peak reflection in X-ray diffraction data. The formation of siliceous hydrogarnet increases with the increase in amorphous nanosilica, but decreases with the increase in hydrated lime content.

In this study, the structure-property relationships of a clay ceramic with calibrated particles (10 or $50\mathrm{\mu m}$) of polymethyl methacrylate (PMMA) were investigated to improve both the thermal and mechanical properties of fired clay bricks incorporating organic wastes. The structure was characterized using differential thermal, thermomechanical, and computed tomography analysis. It was found that the addition of 10- or $50–\mathrm{\mu m}$ particles of PMMA resulted in a same 11% decrease of the thermal conductivity during the extrusion process. The Young’s modulus also increased by 23% during the extrusion process with the addition of $50–\mathrm{\mu m}$ particles. However, the addition of $10–\mathrm{\mu m}$ particles resulted in a greater increase of the Young’s modulus by 34%. The calibrated particles of PMMA were then found to transform into porosity during firing of the clay ceramic. Typically, the pore size of the clay ceramic corresponded to the particle size of the calibrated particles of PMMA. The improvement of the thermal and mechanical properties that was obtained during the extrusion process was conserved in the form of porosity with a reduction of the median pore size after the firing process. Hence, the current results indicate that the thermal and mechanical properties of fired clay bricks can be improved at the same time using a wide range of organic wastes if the organic wastes are subjected to grinding prior to incorporation in the mixture. They also suggest that organic wastes can reduce the environmental impact of fired clay bricks with an energetic contribution of 73.8%.

The first purpose of this paper was to check the applicability of some design methods of fine aggregate matrices (FAM) to modified asphalt binders. Because of shortcomings observed during the replication of those methods, a second objective was outlined: to develop a simpler, less experimental procedure applicable to modified asphalt binders. In the proposed procedure, the binder content of the FAM produced with the neat binder (reference binder content) was determined by means of the concept of specific surface. The binder contents for the FAMs produced with the modified asphalt binders were obtained by multiplying the reference binder content by a ratio that is calculated by dividing the binder content obtained in the design of the hot-mix asphalt (HMA) mixture produced with each modified asphalt binder by the binder content of the HMA mixture produced with the conventional asphalt binder. The ignition method and the method based on the specific surface yielded equivalent reference binder contents. The proposed procedure proved to be efficient and independent of the modified binder used.

Research on the utilization of recycled concrete aggregate (RCA) in civil engineering applications is gaining popularity worldwide due to the increased efforts to promote preservation of the environment and sustainable development. Recycled concrete aggregate concrete is, however, presently still limited to nonstructural applications. Recycled concrete aggregate concrete can still be considered as a rigid pavement material when its flexural strength is improved adequately to sustain future traffic loads. In this study, polyvinyl alcohol (PVA), a water-soluble polymer, was used to improve the flexural strength of RCA concrete. The influence of PVA-to-cement ($p/c$) and water-to-cement ($w/c$) ratios on the compressive and flexural strengths of RCA-PVA concrete was investigated via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Polyvinyl alcohol films were found to retard the hydration process, resulting in the delay in initial and final setting times of cement-PVA paste, therefore reducing the compressive strength of RCA-PVA concrete. For all the $w/c$ ratios tested, the flexural strength increased with increasing $p/c$ ratios up to an optimum $p/c$ ratio that provided the highest flexural strength, followed by a subsequent decrease beyond this peak value. The optimum $p/c$ ratio tended to increase with an increase in $w/c$ ratio, being 0.5, 0.5, 1.0, and 1.5 for $w/c$ ratios of 0.3, 0.4, 0.5, and 0.6, respectively. Based on the requirements of the Department of Highways, Thailand, the $p/c$ $\le 1$ at $w/c$ $\le 0.5$ was found to be suitable for developing RCA-PVA concrete for rigid pavements. The outcome of this research confirms the viability of using PVA to improve the flexural strength of RCA concrete for usage as a sustainable rigid pavement material.

The structural integrity of precast concrete tunnel lining (PCTL) segments largely depends on its durability performance. The ingress of chloride ions into PCTL segments can induce reinforcement corrosion, which has been the primary cause that jeopardizes the structural safety of PCTL. This study explores the mechanical behavior of specimens extracted from full-scale PCTL segments made with conventional steel-rebar-reinforced concrete (RC) and steel-fiber-reinforced concrete (SFRC) for a subway tunnel in Canada and subjected to chloride ions exposure. Test specimens were subjected to chloride ion (${\mathrm{Cl}}^{-}$) solutions with various concentrations (3.5 and 10.0%) for up to 16 months, combined with weekly wetting and drying cycles. The mechanical degradation of RC and SFRC specimens was assessed after every 4 months of chloride ions exposure. Initially, an increase in concrete mass by 0.84 and 0.35% was observed for RC and SFRC PCTL segments, respectively, after 4 months of 3.5% ${\mathrm{Cl}}^{-}$ exposure. However, after 8 months of ${\mathrm{Cl}}^{-}$ exposure, a decreasing trend in mass was observed for both the RC and SRFC specimens. Furthermore, results indicated that the mechanical properties of conventional RC PCTL segments were more vulnerable to chloride-induced damage compared to that of SFRC PCTL segments. For instance, 19 and 47% decreases in compressive and flexural strengths, respectively, were observed in RC specimens after 12 months of exposure to 3.5% ${\mathrm{Cl}}^{-}$ solution. Exposure to 10% ${\mathrm{Cl}}^{-}$ solution led to a greater reduction in the mechanical properties of RC specimens compared to that of 3.5% exposure. No significant decrease in compressive and flexural strengths was observed in SFRC specimens due to ${\mathrm{Cl}}^{-}$ exposure. Interestingly, the mechanical performance of SFRC specimens improved when subjected to chloride ions. Experimental results for both the RC and SFRC segments point to the potential of SFRC as a strong contender in the construction of precast concrete tunnel linings.

Asphalt binder is a thermoplastic material that acts as an elastic solid during rapid load at low service temperatures. There are two main objectives of study to be evaluated, including improvement of local asphalt concrete mixes using crumb rubber and ways to get rid of the accumulated nondecaying scrap tires. Local asphalt concrete mixes can be improved by adding crumb rubber to the asphalt concrete mixes, and the performance of the produced mix was evaluated. Asphalt concrete mixes were designed using the Superpave mix design procedure to effectively evaluate the efficiency of using crumb rubber in asphalt concrete mixes. The improvement in indirect tensile strength, creep resistance, fatigue life, and stripping resistance were used to judge the effectiveness of modification. The modifications made by adding the crumb rubber to the asphalt cement were effective in improving the performance of the properties of hot asphalt concrete mixes and disposing of certain amounts of scrap tires.

Capillary imbibition in brick, stone, and concrete occurs in two stages. The primary process, which occurs in the standard test to measure sorptivity, is a spontaneous imbibition in which air is displaced by the invading liquid (usually water). In primary imbibition, the displacement of air is incomplete, and some air is trapped. The residual air content lies usually in the range 0.1–0.4 of the volume-fraction porosity. Primary imbibition is followed by a much slower secondary process in which trapped air in the interior of the material dissolves in the liquid phase and diffuses to the unsealed external surfaces, where it escapes. As air is lost, there is further imbibition of liquid to replace it. Eventually, all trapped air is lost, and the material reaches saturation. There is current interest in using the rate of secondary imbibition to define a secondary sorptivity, and speculation that this may be a useful property for characterizing porous construction materials, particularly in relation to durability. This paper analyzes the secondary imbibition process and provides a definition of the secondary sorptivity which is independent of the dimensions of the test specimen. The analysis is supported by experimental data on Ancaster and Portland limestone test materials.

This study focuses on using fly ash to produce a cement-free geopolymer concrete. The combination of potassium hydroxide (KOH) and potassium silicate solution (${\mathrm{K}}_2{\mathrm{SiO}}_3$) was used as the alkaline activator to initiate the geopolymerization reaction. The water immersion curing method was used. The concrete specimens were first cured at 60°C for 24 h, followed by ambient temperature curing until testing. The effect of concentration of KOH and the ratio of ${\mathrm{K}}_2{\mathrm{SiO}}_3$ to KOH (PS/PH ratio) on the compressive strength was investigated. The experimental results revealed that the geopolymer concrete activated with 14M KOH solution with the PS/PH of 2.0 exhibited the highest strength. This study also proposes a nondestructive method for the prediction of compressive strength. By using multiple regression technique, an accurate predictive relationship was established between the compressive strength and the longitudinal resonant frequency. The effectiveness and the accuracy of the proposed equation were proven by applying it to a previous study by another researcher.

The difference between hot-mix asphalt (HMA) containing recycled asphalt shingles (RAS) and virgin HMA in terms of composition and properties causes difficulties when engineers try to predict the performance of HMA containing RAS. This study develops a prediction model based on artificial neural networks (ANN) to predict the dynamic modulus ($E^{*}$) of HMA containing RAS. The $E^{*}$ database used in this study to develop the ANN model contains 1,701 sets of experimental data, which were obtained from four different demonstration projects. In order to train and test the model, the data were randomly divided into two different subsets: one is for training, containing 1,361 data points, and the other is for testing, containing 340 data points. The input parameters of the proposed model included percent passing a #200 sieve (${\rho }_{200}$), cumulative percent retained on a #4 sieve (${\rho }_4$), cumulative percent retained on a 9.5-mm sieve (${\rho }_{38}$), cumulative percent retained on a 19-mm sieve (${\rho }_{34}$), air voids ($V_a$), effective binder content ($V_{\mathrm{beff}}$), viscosity of the asphalt binder ($\eta$), loading frequency ($f$), and RAS contents ($p_a$, by weight of total aggregate). The sensitivity analysis of these parameters was performed by correlating each model parameter with $E^{*}$. The proposed ANN model was compared with the Iowa model and showed significantly higher prediction accuracy than the Iowa model. It can be concluded that the proposed ANN model has great potential to be used as a tool to predict the $E^{*}$ of asphalt mixtures containing RAS.

Use of recycled concrete aggregate (RCA) in bituminous paving mixes is limited because of its high water absorption. Therefore, in this study, an attempt has been made to pretreat RCA using bituminous emulsion to reduce its water absorption characteristics, which is referred to in this study as pretreated recycled concrete aggregates (PRCAs). In the second stage, dense bituminous macadam (DBM) paving mixes were prepared using PRCA, RCA, and natural aggregate (NA) as coarse aggregates, with two different types of filler, i.e., cement (CM) and stone dust (SD), and the performance was studied through various tests such as Marshall test parameters, indirect tensile strength, moisture susceptibility, dynamic modulus, and wheel-tracking test for rutting. It was observed that the PRCA and RCA mixtures, in general, satisfy the requirements in terms of Marshall test parameters and moisture susceptibility. Also, from the dynamic modulus and rutting tests, the mixtures containing PRCA showed good results compared with DBM mixes prepared with virgin aggregates. Cement as filler was found to produce better engineering properties compared with stone dust.

Field-cast cementitious grouts are commonly used for connecting adjacent prefabricated bridge deck elements. These grouts can exhibit high shrinkage levels and are susceptible to premature bond failure at the interface between the precast concrete and connection grout. These actions commonly result in connection cracking, which can lead to serviceability issues in the bridge structure such as reinforcing bar corrosion, leakage, and degradation of structural performance. This study presents a set of potential strategies to enhance the shrinkage properties and bond performance of these grouted connections. The strategies include using advanced materials such as ultra-high performance concrete (UHPC), proper detailing of precast concrete connection surfaces, application of internal curing in connection grouts, and use of interface premoistening. The study includes experiments conducted at both material and component levels. At the material level, these potential improvement strategies were evaluated using standardized shrinkage and bond-strength test methods. To demonstrate the impact on structural performance, some of these strategies were used in a component-level investigation consisting of three large-scale bridge deck connection tests. Experimental results demonstrate that the suggested strategies can reduce shrinkage, enhance bond strength, and improve structural performance of connections.

This study investigates and evaluates the storage stability of asphalt binder modified by bio-oil at high temperature. Five bio-asphalts are prepared by adding 10, 15, 20, 25, and 30% bio-oil into 70# petroleum asphalt. The bioasphalts are statically stored for 48 h at four different temperatures: 120, 140, 160, and 180°C. The softening point test, rotational viscosity test, dynamic shear rheometer (DSR) test, and Fourier transform infrared spectroscopy (FTIR) test are applied. The top and bottom sections of samples after thermal storage are analyzed for thermal storage stability from three aspects: physical properties, rheological properties, and functional group composition. The results show that after thermal storage, the bioasphalts segregated and the softening point, viscosity, and antirutting factor of the bottom sections are larger than those of the top sections. The viscosities of the top and bottom sections of bioasphalt with 20% bio-oil are 0.507 and $0.643\mathrm{Pa}·\mathrm{s}$, respectively, under the storage temperature of 140°C. Moreover, the thermal storage stability of bioasphalts decreases with an increase in bio-oil content and storage temperature. Furthermore, based on rheological properties and functional group analysis, it is found that physical segregation and chemical reactions occurred, such as carbonation reactions, reactions between the oligomers, and volatilization of aromatic compounds. Overall, it is recommended that the storage temperature should be kept below 160°C and the bio-oil content should be less than 25%.

Over the last few decades, the high growth rate in China’s construction industry has increased the demand for building materials. Thus, the sustainable use and conservation of quality clay soil for brick production has attracted much attention in recent years. This paper investigates the technical feasibility of using saline soil as a raw material for the production of autoclaved lime-saline soil products. The reactivity of lime-saline soil under different autoclave temperatures (120, 150, and 175°C), pressures (0.10, 0.38, and 0.78 MPa), and times (1, 2, 3, and 6 h) was assessed. The experimental results indicate that saline soil’s reactivity increased with increasing lime content as well as autoclave temperature, pressure, and reaction time. However, the reaction process seemed to be significant only for the first 2 h. The mixture proportions were varied to further examine the effects of sand sizes and their replacement content for saline soil on the properties of autoclaved specimens. It was observed that specimens containing 25–85% saline soil possessed compressive strength ranging from 17 to 36 MPa with relatively low water absorption (4.0–6.8%). Thermal analysis results indicate that tobermorite is responsible for the higher mechanical strength gain for the autoclaved specimens. The overall results have proved that it is feasible to produce an autoclaved lime-saline soil product with a lower environmental impact.

Québec roads are subjected to seasonal ambient temperature variations and daily rapid variations of temperature. These significant temperature variations in combination with the moisture inside the pores result in the development of premature deterioration in asphalt pavement. At present, the effect of regional freeze-thaw cycles on fatigue cracking has not been considered in the Mechanistic-empirical pavement design guide method or other design methods in cold regions, whose results overestimate the pavement life. Hence, the main objective of this study was to conduct the thermomechanical tests on an asphalt mixture before and after rapid freeze-thaw cycles. Considering the differences regarding the 2S2P1D model parameters, it was found that the influence of freeze-thaw conditions on the stiffness behavior of the mix is higher when increasing the number of cycles from 150 to 300. Regarding fatigue test results, the reference mixture was more resistant to fatigue cracking than the conditioned mix after 300 freeze-thaw cycles.

Roller-compacted concrete (RCC) is widely used in civil engineering, and its compressive behavior is commonly agreed to be affected by thin layers and the vibration rolling technique, which is different from conventional concrete, especially under high strain rates. However, experiments on RCC material under intermediate to high strain rates are relatively limited. In this paper, new empirical relations are proposed for dynamic compressive parameters of RCC specimens based on testing data via $\mathrm{\varphi }100\text{-}\mathrm{mm}$ split Hopkinson pressure bar (SHPB). Additionally, the damage patterns under different strain rates are described, and strain-rate sensitivity, aggregate-grade effects, and size effects are tested and analyzed. The results indicate that heterogeneity and thin layers in the specimen composites play apparent roles in the dynamic compressive characteristics of RCC material. The stress-strain curve of RCC has a plateau at approximately $\pm 30\%$ of the critical strain, and the dynamic compressive strength, critical strain, and specific energy absorption (SEA) all increase with increasing strain rate, indicating fine ductility and effective energy absorption compared with conventional concrete.

The impact acoustic test is a fast and low-cost nondestructive alternative to evaluate the mechanical properties of concrete. However, the dynamic elastic modulus obtained in this test differs systematically from the static one. The aim of this paper is to study this relationship as well as to identify possible advantages and limitations of impact acoustics in comparison to compression tests until the age of 28 days. Seventeen concrete mixtures were prepared, obtaining compressive strengths ranging from 13 to 147 MPa. Acoustic and compression tests were performed at different ages (typically 3, 7, 14, and 28 days). The results obtained from impact acoustics showed lower dispersion [average coefficient of variation $(\mathrm{CV})=1.53\%$], better representation of maturity over time ($R^2=0.75$), and excellent correlation to compressive strength ($R^2=0.88$) and static elastic modulus ($R^2=0.75$). This technique has the potential of application to evaluate the evolution of the mechanical properties of concrete over time in the prestress concrete industry.